Surface acoustic wave device having mass-loaded electrode

ABSTRACT

Surface acoustic wave device having mass-loaded electrode. In some embodiments, a surface acoustic wave device for providing resonance of a surface acoustic wave having a wavelength λ can include a quartz substrate and a piezoelectric plate formed from LiTaO3 or LiNbO3 disposed over the quartz substrate. The piezoelectric plate can have a thickness greater than 2λ. The surface acoustic wave device can further include an interdigital transducer electrode formed over the piezoelectric plate. The interdigital transducer electrode can have a mass density ρ in a range 1.50 g/cm3&lt;ρ≤6.00 g/cm3, 6.00 g/cm3&lt;ρ≤12.0 g/cm3, or 12.0 g/cm3&lt;ρ≤23.0 g/cm3, and a thickness greater than 0.148λ, greater than 0.079λ, or greater than 0.036λ, respectively.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application No.62/901,202 filed Sep. 16, 2019, entitled SURFACE ACOUSTIC WAVE DEVICEHAVING MASS-LOADED ELECTRODE, the disclosure of which is herebyexpressly incorporated by reference herein in its entirety.

BACKGROUND Field

The present disclosure relates to acoustic wave devices such as surfaceacoustic wave (SAW) devices.

Description of the Related Art

A surface acoustic wave (SAW) resonator typically includes aninterdigital transducer (IDT) electrode implemented on a surface of apiezoelectric layer. Such an electrode includes two interdigitized setsof fingers, and in such a configuration, the distance between twoneighboring fingers of the same set is approximately the same as thewavelength λ of a surface acoustic wave supported by the IDT electrode.

In many applications, the foregoing SAW resonator can be utilized as aradio-frequency (RF) filter based on the wavelength λ. Such a filter canprovide a number of desirable features.

SUMMARY

In accordance with some implementations, the present disclosure relatesto a surface acoustic wave device for providing resonance of a surfaceacoustic wave having a wavelength λ. The surface acoustic wave deviceincludes a quartz substrate and a piezoelectric plate formed from LiTaO₃or LiNbO₃ and disposed over the quartz substrate. The piezoelectricplate has a thickness greater than 2λ. The surface acoustic wave devicefurther includes an interdigital transducer electrode formed over thepiezoelectric plate. The interdigital transducer electrode has a massdensity ρ in a range 1.50 g/cm³<ρ≤6.00 g/cm³, 6.00 g/cm³<ρ≤12.0 g/cm³,or 12.0 g/cm³<ρ≤23.0 g/cm³, and a thickness greater than 0.148λ, greaterthan 0.079λ, or greater than 0.036λ, respectively.

In some embodiments, the interdigital transducer electrode can have ametallization ratio (MR) of approximately 0.5, where MR=F/(F+G), withthe quantity F being a width of an electrode finger and the quantity Gbeing a gap dimension between two electrode fingers. In someembodiments, the interdigital transducer electrode can include aluminum,titanium, magnesium, copper, nickel, silver, molybdenum, gold, platinum,tungsten, tantalum, hafnium, other metal, an alloy formed from aplurality of metals, or a structure having a plurality of layers, with amass density range 1.50 g/cm³<ρ≤23.0 g/cm³.

In some embodiments, the piezoelectric plate can be a LiTaO₃ (LT) plate.The LT plate can be configured with Euler angles of (0−/+5°, 80 to 155°,0/+5), (90−/+5°, 90°−/+5°, 0 to 180°), or orientation angles equivalentthereto.

In some embodiments, the piezoelectric plate can be a LiNbO₃ (LN) plate.The LN plate can be configured with Euler angles of (0−/+5°, 60 to 160°,0−+5), (90−/+5°, 90°−/+5°, 0 to 180°), or orientation angles equivalentthereto.

In some embodiments, the quartz substrate can be configured with Eulerangles of (0+/−5°, θ, 35°+/−8°), (10°+/−±5°, θ, 42°+/−8°), (20°+/−5°, θ,50°+/−8°), (0°+/−5°, θ, 0+/−50), (10°+/−5°, θ, 0+/−50), (20°+/−5°, θ,0+/−50), (0°+/−5°, θ, 90°+/−5°), (10°+/−5°, θ, 90°+/−5°), (20°+/−5°, θ,90°+/−5°), (90°+/−5°, 90°+/−5°, ψ), or orientation angles equivalentthereto, where each of θ and ψ has a value in a range 0 to 180°.

In some implementations, the present disclosure relates to a method formanufacturing a surface acoustic wave device that provides resonance ofa surface acoustic wave having a wavelength λ. The method includesforming or providing a quartz substrate, and implementing apiezoelectric plate formed from LiTaO₃ or LNbO₃ to be over the quartzsubstrate, such that the piezoelectric plate has a thickness greaterthan 2λ. The method further includes forming an interdigital transducerelectrode over the piezoelectric plate, such that the interdigitaltransducer electrode has a mass density ρ in a range 1.50 g/cm³<ρ≤6.00g/cm³, 6.00 g/cm³<ρ≤12.0 g/cm³, or 12.0 g/cm³<ρ≤23.0 g/cm³, and athickness greater than 0.148λ, greater than 0.079λ, or greater than0.036λ, respectively.

In some embodiments, the implementing of the piezoelectric plate caninclude forming or providing an assembly of a relatively thickpiezoelectric plate and a quartz plate. The implementing of thepiezoelectric plate can further include performing a thinning process onthe relatively thick piezoelectric plate to provide the piezoelectricplate with the thickness greater than 2λ, such that the piezoelectricplate includes a first surface that engages with the quartz plate and asecond surface, opposite from the first surface, resulting from thethinning process.

In some embodiments, the thinning process can include a polishingprocess. In some embodiments, the forming of the interdigital transducerelectrode over the piezoelectric plate can include forming theinterdigital transducer electrode on the second surface of thepiezoelectric plate. In some embodiments, the quartz plate of theassembly can be substantially the same as the quartz substrate.

In some embodiments, the implementing of the piezoelectric plate caninclude forming or providing an assembly of a relatively thickpiezoelectric plate and a handling substrate. The implementing of thepiezoelectric plate can further include performing a thinning process onthe relatively thick piezoelectric plate to provide a thinnedpiezoelectric plate with a thickness greater than 2λ, such that thethinned piezoelectric plate includes a first surface resulting from thethinning process and a second surface, opposite from the first surface,that engages the handling substrate. The thinning process can include,for example, a polishing process.

In some embodiments, the implementing of the piezoelectric plate canfurther include attaching a quartz plate to the first surface of thethinned piezoelectric plate. The implementing of the piezoelectric platecan further include removing the handling substrate to expose the secondsurface of the thinned piezoelectric plate. The removing of the handlingsubstrate can include, for example, an etching process.

In some embodiments, the forming of the interdigital transducerelectrode over the piezoelectric plate can include forming theinterdigital transducer electrode on the exposed second surface of thepiezoelectric plate. In some embodiments, the quartz plate attached tothe first surface of the piezoelectric plate can be substantially thesame as the quartz substrate.

In a number of implementations, the present disclosure relates to aradio-frequency filter that includes an input node for receiving asignal and an output node for providing a filtered signal. Theradio-frequency filter further includes a surface acoustic waveimplemented to be electrically between the input node and the outputnode. The surface acoustic wave device is configured to provideresonance of a surface acoustic wave having a wavelength λ, and includesa quartz substrate and a piezoelectric plate formed from LiTaO₃ orLiNbO₃ and disposed over the quartz substrate. The piezoelectric platehas a thickness greater than 2λ. The surface acoustic wave devicefurther includes an interdigital transducer electrode formed over thepiezoelectric plate. The interdigital transducer electrode has a massdensity ρ in a range 1.50 g/cm³<ρ≤6.00 g/cm³, 6.00 g/cm³<ρ≤12.0 g/cm³,or 12.0 g/cm³<ρ≤23.0 g/cm³, and a thickness greater than 0.148λ, greaterthan 0.079λ, or greater than 0.036λ, respectively.

According to a number of implementations, the present disclosure relatesto a radio-frequency module that includes a packaging substrateconfigured to receive a plurality of components, and a radio-frequencycircuit implemented on the packaging substrate and configured to supporteither or both of transmission and reception of signals. Theradio-frequency module further includes a radio-frequency filterconfigured to provide filtering for at least some of the signals. Theradio-frequency filter includes a surface acoustic wave deviceconfigured to provide resonance of a surface acoustic wave having awavelength λ and including a quartz substrate and a piezoelectric plateformed from LiTaO₃ or LiNbO₃ and disposed over the quartz substrate. Thepiezoelectric plate has a thickness greater than 2λ. The surfaceacoustic wave device further includes an interdigital transducerelectrode formed over the piezoelectric plate. The interdigitaltransducer electrode has a mass density ρ in a range 1.50 g/cm³<ρ≤6.00g/cm³, 6.00 g/cm³<ρ≤12.0 g/cm³, or 12.0 g/cm³<ρ≤23.0 g/cm³, and athickness greater than 0.148λ, greater than 0.079λ, or greater than0.036λ, respectively.

In some teachings, the present disclosure relates to a wireless devicethat includes a transceiver, an antenna, and a wireless systemimplemented to be electrically between the transceiver and the antenna.The wireless system includes a filter configured to provide filteringfunctionality for the wireless system. The filter includes a surfaceacoustic wave device configured to provide resonance of a surfaceacoustic wave having a wavelength λ and including a quartz substrate anda piezoelectric plate formed from LiTaO₃ or LiNbO₃ and disposed over thequartz substrate. The piezoelectric plate has a thickness greater than2λ. The surface acoustic wave device further includes an interdigitaltransducer electrode formed over the piezoelectric plate. Theinterdigital transducer electrode has a mass density ρ in a range 1.50g/cm³<ρ≤6.00 g/cm³, 6.00 g/cm³<ρ≤12.0 g/cm³, or 12.0 g/cm³<ρ≤23.0 g/cm³,and a thickness greater than 0.148λ, greater than 0.079λ, or greaterthan 0.036λ, respectively.

According to some implementations, the present disclosure relates to asurface acoustic wave device for providing resonance of a surfaceacoustic wave having a wavelength λ. The surface acoustic wave deviceincludes a quartz substrate and a piezoelectric plate formed from LiTaO₃or LiNbO₃ and disposed over the quartz substrate. The piezoelectricplate has a thickness greater than 2λ. The surface acoustic wave devicefurther includes an interdigital transducer electrode formed over thepiezoelectric plate. The interdigital transducer electrode has a massdensity ρ and a thickness T greater than

${T_{threshold} = {\left( \frac{0.5}{MR} \right)\left\lbrack {a - {b\left( {1 - e^{{- \rho}\text{/}c}} \right)}} \right\rbrack}},$with the quantity MR being a metallization ratio of the interdigitaltransducer electrode, the quantity a having a value of 0.19091λ±δ_(a),the quantity b having a value of 0.17658λ±δ_(b), and the quantity chaving a value of 9.08282 g/cm³±δ_(c).

In some embodiments, the metallization ratio (MR) of the interdigitaltransducer electrode can be estimated as F/(F+G), with the quantity Fbeing a width of an electrode finger and the quantity G being a gapdimension between two electrode fingers. In some embodiments, themetallization ratio (MR) can have a value of approximately 0.5.

In some embodiments, the quantity δ_(a) can have a value of(0.10)0.19091λ, (0.09)0.19091λ, (0.08)0.19091λ, (0.07)0.19091λ,(0.06)0.19091λ, (0.05)0.19091λ, (0.04)0.19091λ, (0.03)0.19091λ,(0.02)0.19091λ, (0.01)0.19091λ, or approximately zero. In someembodiments, the quantity δ_(b) can have a value of (0.10)0.17658λ,(0.09)0.17658λ, (0.08)0.17658λ, (0.07)0.17658λ, (0.06)0.17658λ,(0.05)0.17658λ, (0.04)0.17658λ, (0.03)0.17658λ, (0.02)0.17658λ,(0.01)0.17658λ, or approximately zero. In some embodiments, the quantityδ_(c) can have a value of (0.10)9.08282 g/cm³, (0.09)9.08282 g/cm³,(0.08)9.08282 g/cm³, (0.07)9.08282 g/cm³, (0.06)9.08282 g/cm³,(0.05)9.08282 g/cm³, (0.04)9.08282 g/cm³, (0.03)9.08282 g/cm³,(0.02)9.08282 g/cm³, (0.01)9.08282 g/cm³, or approximately zero.

In some embodiments, the piezoelectric plate can be a LiTaO₃ (LT) plate.In some embodiments, the LT plate can be configured with Euler angles of(0-/+5°, 80 to 155°, 0−/+5°), (90−/+5°, 90°−/+5°, 0 to 180°), ororientation angles equivalent thereto.

In some embodiments, the piezoelectric plate can be a LiNbO₃ (LN) plate.The LN plate can be configured with Euler angles of (0−/+5°, 60 to 160°,0/+5), (90−/+5°, 90°−/+5°, 0 to 180°), or orientation angles equivalentthereto.

In some embodiments, the quartz substrate can be configured with Eulerangles of (0+/−5°, θ, 35°+/−8°), (10°+/−±5°, θ, 42°+/−8°), (20°+/−5°, θ,50°+/−8°), (0°+/−5°, θ, 00+/−50), (10°+/−5°, θ, 0+/−50), (20°+/−5°, θ,0+/−5), (0°+/−5°, θ, 90°+/−5°), (10°+/−5°, θ, 90°+/−5°), (20°+/−5°, θ,90°+/−5°), (90°+/−5°, 90°+/−5°, ψ), or orientation angles equivalentthereto, where each of θ and ψ has a value in a range 0 to 180°.

In some teachings, the present disclosure relates to a method formanufacturing a surface acoustic wave device that provides resonance ofa surface acoustic wave having a wavelength λ. The method includesforming or providing a quartz substrate. The method further includesimplementing a piezoelectric plate formed from LiTaO₃ or LiNbO₃ to beover the quartz substrate, such that the piezoelectric plate has athickness greater than 2λ. The method further includes forming aninterdigital transducer electrode over the piezoelectric plate, suchthat the interdigital transducer electrode has a mass density ρ and athickness T greater than

${T_{threshold} = {\left( \frac{0.5}{MR} \right)\left\lbrack {a - {b\left( {1 - e^{{- \rho}\text{/}c}} \right)}} \right\rbrack}},$the quantity MR being a metallization ratio of the interdigitaltransducer electrode, the quantity a having a value of 0.19091λ±δ_(a),the quantity b having a value of 0.17658λ±δ_(b), and the quantity chaving a value of 9.08282 g/cm³±δ_(c).

In some embodiments, the implementing of the piezoelectric plate caninclude forming or providing an assembly of a relatively thickpiezoelectric plate and a quartz plate. The implementing of thepiezoelectric plate can further include performing a thinning process onthe relatively thick piezoelectric plate to provide the piezoelectricplate with the thickness greater than 2λ, such that the piezoelectricplate includes a first surface that engages with the quartz plate and asecond surface, opposite from the first surface, resulting from thethinning process. The thinning process can include, for example, apolishing process.

In some embodiments, the forming the interdigital transducer electrodeover the piezoelectric plate can include forming the interdigitaltransducer electrode on the second surface of the piezoelectric plate.In some embodiments, the quartz plate of the assembly can besubstantially the same as the quartz substrate.

In some embodiments, the implementing of the piezoelectric plate caninclude forming or providing an assembly of a relatively thickpiezoelectric plate and a handling substrate. The implementing of thepiezoelectric plate can further include performing a thinning process onthe relatively thick piezoelectric plate to provide a thinnedpiezoelectric plate with a thickness greater than 2λ, such that thethinned piezoelectric plate includes a first surface resulting from thethinning process and a second surface, opposite from the first surface,that engages the handling substrate. The thinning process include, forexample, a polishing process.

In some embodiments, the implementing of the piezoelectric plate canfurther include attaching a quartz plate to the first surface of thethinned piezoelectric plate. The implementing of the piezoelectric platecan further include removing the handling substrate to expose the secondsurface of the thinned piezoelectric plate. The removing of the handlingsubstrate include, for example, an etching process.

In some embodiments, the forming the interdigital transducer electrodeover the piezoelectric plate can include forming the interdigitaltransducer electrode on the exposed second surface of the piezoelectricplate. In some embodiments, the quartz plate attached to the firstsurface of the piezoelectric plate can be substantially the same as thequartz substrate.

In accordance with some implementations, the present disclosure relatesto a radio-frequency filter that includes an input node for receiving asignal and an output node for providing a filtered signal. Theradio-frequency filter further includes a surface acoustic wave deviceimplemented to be electrically between the input node and the outputnode. The surface acoustic wave device is configured to provideresonance of a surface acoustic wave having a wavelength λ and includesa quartz substrate and a piezoelectric plate formed from LiTaO₃ orLiNbO₃ and disposed over the quartz substrate. The piezoelectric platehas a thickness greater than 2λ. The surface acoustic wave devicefurther includes an interdigital transducer electrode formed over thepiezoelectric plate. The interdigital transducer electrode has a massdensity ρ and a thickness T greater than

${T_{threshold} = {\left( \frac{0.5}{MR} \right)\left\lbrack {a - {b\left( {1 - e^{{- \rho}\text{/}c}} \right)}} \right\rbrack}},$with the quantity MR being a metallization ratio of the interdigitaltransducer electrode, the quantity a having a value of 0.19091λ±δ_(a),the quantity b having a value of 0.17658λ+δ_(b), and the quantity chaving a value of 9.08282 g/cm³±δ_(c).

In some implementations, the present disclosure relates to aradio-frequency module that includes a packaging substrate configured toreceive a plurality of components, and a radio-frequency circuitimplemented on the packaging substrate and configured to support eitheror both of transmission and reception of signals. The radio-frequencymodule further includes a radio-frequency filter configured to providefiltering for at least some of the signals. The radio-frequency filterincludes a surface acoustic wave device configured to provide resonanceof a surface acoustic wave having a wavelength λ. The surface acousticwave device includes a quartz substrate and a piezoelectric plate formedfrom LiTaO₃ or LiNbO₃ and disposed over the quartz substrate. Thepiezoelectric plate has a thickness greater than 2λ. The surfaceacoustic wave device further includes an interdigital transducerelectrode formed over the piezoelectric plate. The interdigitaltransducer electrode has a mass density ρ and a thickness T greater than

${T_{threshold} = {\left( \frac{0.5}{MR} \right)\left\lbrack {a - {b\left( {1 - e^{{- \rho}\text{/}c}} \right)}} \right\rbrack}},$with the quantity MR being a metallization ratio of the interdigitaltransducer electrode, the quantity a having a value of 0.19091λ±δ_(a),the quantity b having a value of 0.17658λ±δ_(b), and the quantity chaving a value of 9.08282 g/cm³±δ_(c).

In some teachings, the present disclosure relates to a wireless devicethat includes a transceiver, an antenna, and a wireless systemimplemented to be electrically between the transceiver and the antenna.The wireless system includes a filter configured to provide filteringfunctionality for the wireless system. The filter includes a surfaceacoustic wave device configured to provide resonance of a surfaceacoustic wave having a wavelength λ. The surface acoustic wave deviceincludes a quartz substrate and a piezoelectric plate formed from LiTaO₃or LiNbO₃ and disposed over the quartz substrate. The piezoelectricplate has a thickness greater than 2λ. The surface acoustic wave devicefurther includes an interdigital transducer electrode formed over thepiezoelectric plate. The interdigital transducer electrode has a massdensity ρ and a thickness T greater than

${T_{threshold} = {\left( \frac{0.5}{MR} \right)\left\lbrack {a - {b\left( {1 - e^{{- \rho}\text{/}c}} \right)}} \right\rbrack}},$with the quantity MR being a metallization ratio of the interdigitaltransducer electrode, the quantity a having a value of 0.19091λ±δ_(a),the quantity b having a value of 0.17658λ+δ_(b), and the quantity chaving a value of 9.08282 g/cm³±δ_(c).

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a surface acoustic wave device that includes a transducerimplemented on a piezoelectric material, such that when anelectromagnetic (EM) energy is applied to the piezoelectric materialthrough the transducer, some or all of the EM energy is converted to anacoustic energy that propagates from the transducer as surface acousticwaves.

FIG. 2 shows that the surface acoustic wave device of FIG. 1 can alsofunction in reverse, such that some or all of an acoustic energyassociated with surface acoustic waves supported by a piezoelectricmaterial is converted to an EM energy through the transducer.

FIG. 3 shows that in some embodiments, a surface acoustic wave devicecan include a tuned electrode configured to provide some or all of thetransducer functionalities of FIGS. 1 and 2.

FIG. 4 shows an example of a surface acoustic wave device where a tunedelectrode is implemented as an interdigital transducer (IDT) on asurface of a piezoelectric layer having a thickness T.

FIG. 5 shows an example of a surface acoustic wave (SAW) deviceimplemented as a SAW resonator.

FIG. 6 shows an enlarged and isolated plan view of the IDT electrode ofthe SAW resonator of FIG. 5.

FIG. 7 shows a sectional view as indicated in FIG. 6.

FIGS. 8A to 8C show an example of a thinning process that can beutilized to obtain a thin piezoelectric plate such as a thin LiTaO₃ (LT)plate.

FIGS. 9A to 9E show another example of a thinning process that can beutilized to obtain a thin piezoelectric plate such as a thin LiTaO₃ (LT)plate.

FIG. 10A shows an example of a SAW resonator that can be formed byeither of the processes of FIGS. 8A to 8C and FIGS. 9A to 9E.

FIG. 10B shows another example of a SAW resonator that can be formed byeither of the processes of FIGS. 8A to 8C and FIGS. 9A to 9E.

FIGS. 11A to 11D show examples where a thick LT plate can be preferableover a thin LT plate.

FIG. 12 shows an example of a SAW resonator having an LT plate with aquartz plate attached on one side, and an electrode formed on the otherside.

FIG. 13 shows an impedance characteristic plot for the SAW resonator ofFIG. 12.

FIG. 14 shows another example of a SAW resonator having an LT plate witha quartz plate attached on one side, and an electrode formed on theother side.

FIG. 15 shows an impedance characteristic plot for the SAW resonator ofFIG. 14.

FIG. 16 shows yet another example of a SAW resonator having an LT platewith a quartz plate attached on one side, and an electrode formed on theother side.

FIG. 17 shows an impedance characteristic plot for the SAW resonator ofFIG. 16.

FIG. 18 shows yet another example of a SAW resonator having an LT platewith a quartz plate attached on one side, and an electrode formed on theother side.

FIG. 19 shows an impedance characteristic plot for the SAW resonator ofFIG. 18.

FIG. 20 shows impedance ratio plots as a function of LT plate thickness,for different copper (Cu) electrode thicknesses.

FIG. 21 shows impedance ratio plots as a function of LT plate thickness,for different aluminum (Al) electrode thicknesses.

FIG. 22 shows impedance ratio plots as a function of piezoelectricthickness for a SAW resonator with a more generalized combination of apiezoelectric plate and an electrode implemented thereon.

FIG. 23 depicts an example of a relationship between thickness thresholdvalue of an electrode and density of the electrode material includingaluminum, copper and gold.

FIG. 24 depicts another example of a relationship between thicknessthreshold value of an electrode and density of the electrode materialincluding a number of materials.

FIG. 25 shows that in some embodiments, multiple units of SAW resonatorscan be fabricated while in an array form.

FIG. 26 shows that in some embodiments, a SAW resonator having or morefeatures as described herein can be implemented as a part of a packagedevice.

FIG. 27 shows that in some embodiments, the SAW resonator based packageddevice of FIG. 26 can be a packaged filter device.

FIG. 28 shows that in some embodiments, a radio-frequency (RF) modulecan include an assembly of one or more RF filters.

FIG. 29 depicts an example wireless device having one or moreadvantageous features described herein.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

FIG. 1 depicts a surface acoustic wave device 10 that includes atransducer 12 implemented on a piezoelectric material 14. When anelectromagnetic (EM) energy is applied to the piezoelectric material 14through the transducer 12, some or all of the EM energy is converted toan acoustic energy; and at least some of such an acoustic energypropagates from the transducer 12 as surface acoustic waves 16.

FIG. 2 shows that the surface acoustic wave device 10 can also functionin reverse, such that some or all of acoustic energy associated withsurface acoustic waves 18 supported by a piezoelectric material 14 areconverted to an EM energy through a transducer 12. It is noted that thetransducer 12 of FIG. 2 can be the same transducer 12 as in FIG. 1, or aseparate transducer in addition to the transducer 12 of FIG. 1. In thelatter configuration where two transducers are provided, thecorresponding surface acoustic wave device can be utilized as, forexample, a surface acoustic wave filter. In such an application, thetransducers 12 can be configured such that the surface acoustic wave hasa resonance frequency selected such that the incoming EM energy in theform of an EM signal is filtered to provide a frequency for the outgoingEM energy that corresponds to the resonance frequency of the surfaceacoustic wave.

FIG. 3 shows that in some embodiments, a surface acoustic wave device100 can include a tuned electrode 102 configured to provide thetransducer functionality of FIGS. 1 and 2. More particularly, the tunedelectrode 102 can be configured such that a surface acoustic wave 106(travelling away from the electrode 102 or travelling to the electrode102) supported by a piezoelectric material 104 has desirable performancecharacteristics for a given volume 108 of the piezoelectric material104. In the context of the example filtering application, such desirableperformance characteristics of the surface acoustic wave 106 can resultin the corresponding filtered EM signal to also have desirableperformance characteristics.

It is noted that if an electrode is not tuned for a volume such as thevolume 108, acoustic energy driven into the volume 108 or received fromthe volume 108 can result in the electrode being undesirably impacted ina physical manner. In such a situation, the resulting EM signal caninclude undesirable noises and/or other artifacts, thereby degrading theperformance of the corresponding surface acoustic device.

Thus, in some embodiments, the tuned electrode 102 of FIG. 3 can beconfigured to be physically stable as acoustic energy is driven into orreceived from the volume 108 of the piezoelectric material 104. In someembodiments, such physically stable feature of the tuned electrode 102can be provided by the electrode 102 being appropriately massive,depending on one or more factors such a material used for thepiezoelectric 104 and the size of the volume 108. For the purpose ofdescription, such an appropriately massive feature of the tunedelectrode 102 may be referred to herein as being mass-loaded. Examplesof how electrodes can be mass-loaded are described herein in greaterdetail.

FIG. 4 shows an example of a surface acoustic wave device 100 where atuned electrode 102 is implemented as an interdigital transducer (IDT)on a surface 110 of a piezoelectric layer 104 having a thickness T. Insuch a configuration, a first set of one or more fingers can be arrangedin an interdigitized manner with a second set of one or more fingers.When an EM signal such as a radio-frequency (RF) signal (having afrequency f_(RF)) is applied to respective terminals of the first andsecond sets of fingers, a surface acoustic wave 108 having a wavelengthλ_(ACOUSTIC) is generated in the piezoelectric layer 104. In reverse,when a surface acoustic wave 108 having a wavelength λ_(ACOUSTIC) isincident on the first and second sets of fingers, an RF signal having afrequency f_(RF) is generated on the respective terminals. It is notedthat in the foregoing configuration, the wavelength λ_(ACOUSTIC) isapproximately the same as the distance between two neighboring fingersof the same set.

As shown in FIG. 4, the piezoelectric layer 104 has a thickness T whichcan be a design factor for which the electrode 102 can be tuned.Examples of such tuning of the electrode 102 based at least in part onthe thickness (T) of the piezoelectric layer 104 are described herein ingreater detail.

FIG. 5 shows an example of a surface acoustic wave (SAW) device 100implemented as a SAW resonator. Such a SAW resonator can include apiezoelectric layer 104 formed of, for example, LiTaO₃ (also referred toherein as lithium tantalate or LT) or LiNbO₃ (also referred to herein aslithium niobate or LN). Such a piezoelectric layer can include a firstsurface 110 (e.g., an upper surface when the SAW resonator 100 isoriented as shown) and an opposing second surface. The second surface ofthe piezoelectric layer 104 can be attached to, for example, a quartzsubstrate 112.

On the first surface 110 of the piezoelectric layer 104, an interdigitaltransducer (IDT) electrode 102 can be implemented, as well as one ormore reflector assemblies (e.g., 114, 116). FIG. 6 shows an enlarged andisolated plan view of the example IDT electrode 102 of the SAW resonator100 of FIG. 5. It will be understood that the IDT electrode 102 of FIGS.5 and 6 can included more or less numbers of fingers for the twointerdigitized sets of fingers.

In the example of FIG. 6, the IDT electrode 102 is shown to include afirst set 120 a of fingers 122 a and a second set 120 b of fingers 122 barranged in an interdigitized manner. As described herein, the distancebetween two neighboring fingers of the same set (e.g., neighboringfingers 122 a of the first set 120 a) is approximately the same as thewavelength λ of a surface acoustic wave associated with the IDTelectrode 102.

In the example of FIG. 6, various dimensions associated with the fingersare shown. More particularly, each finger (122 a or 122 b) is shown tohave a lateral width of F, and a gap distance of G is shown to beprovided between two interdigitized neighboring fingers (122 a and 122b).

FIG. 7 shows a sectional view as indicated in FIG. 6. The indicateddimensions F and G are as described in reference to FIG. 6, and eachfinger (122 a or 122 b) is shown to have a thickness of T_(electrode).FIG. 7 also shows that the piezoelectric layer 104 has a thickness ofT_(piezoelectric).

It is noted that a SAW resonator 100 as described in reference to FIGS.5-7 can be configured to provide, for example, excellent filteringfunctionality. As an example, it is noted that mobile phones andsmartphones utilize many frequency bands (e.g., almost eighty bands) andsome or all of such frequency bands are congested at 3.4 GHz or lower,such that adjacent bands are very narrowly separated in frequency.Accordingly, there is an intense need or desire for RF filters havingsteeper and better temperature characteristics to prevent interferencebetween adjacent bands.

In some embodiments, a filter providing a desired temperaturecharacteristic, a higher Q, and/or a higher impedance ratio, can includea LiTaO₃ (also referred to herein as LT) thin plate or a LNbO₃ (alsoreferred to herein as LN) thin plate that has a negative thermalcoefficient of frequency (TCF) combined with quartz having orientationangles for a positive TCF. With such a configuration, desiredperformance features such as an improved TCF and a higher impedanceratio can be obtained. However, the LT or LN plate is typicallyrelatively thin (e.g., thinner than approximately 1 μm). Such a thin LTor LN plate can be obtained by a thinning process. Accordingly, problemssuch as yield and/or cost may arise during the thinning process such asa polishing process.

Various examples are described herein in the context of a piezoelectriclayer or plate being an LT layer or plate. It will be understood thatone or more features of the present disclosure can also be implementedwith other piezoelectric layers or plates, including, for example, an LNlayer or plate.

FIGS. 8A-8C show an example of a thinning process that can be utilizedto obtain the above-described thin LT plate. It will be understood thatthe example thinning process of FIGS. 8A-8C can also be utilized toobtain an LT plate associated with a tuned electrode having one or morefeatures as described herein.

FIGS. 9A-9E show another example of a thinning process that can beutilized to obtain the above-described thin LT plate. It will beunderstood that the example thinning process of FIGS. 9A-9E can also beutilized to obtain an LT plate associated with a tuned electrode havingone or more features as described herein.

In the first example, FIG. 8A shows that in some embodiments, a thinningprocess can include a process step where an assembly 132 of a relativelythick LT plate 130 and a quartz plate 112 is formed or provided.

FIG. 8B shows a process step where the thickness of the relatively thickLT plate 130 is reduced to a thinner LT plate 134, so as to form anassembly 136. In some embodiments, such a thinning process step can beachieved by, for example, polishing process such as a mechanicalpolishing process, a chemical mechanical process, etc. In FIG. 8B, thethinner LT plate 134 is shown to include a first surface that engageswith the quartz plate 112 (directly or through an intermediate layer),and a second surface, opposite from the first surface, resulting fromthe thinning process step.

FIG. 8C shows a process step where an electrode 102 is formed on thesecond surface of the LT plate 134, so as to form an assembly 138. Asdescribed herein, such an electrode can include an interdigitizedarrangement of fingers 122 a, 122 b.

In some embodiments, some or all of the process steps associated withFIGS. 8A-8C can be implemented for an individual unit to produce asingle unit of the assembly 138, implemented for a plurality ofindividual units to produce a plurality of respective single units ofassemblies 138, implemented while a plurality units are attached in anarray format (e.g., wafer format) followed by singulation to produce aplurality of singulated units of assemblies 138, or some combinationthereof.

In the second example, FIG. 9A shows that in some embodiments, athinning process can include a process step where an assembly 142 of arelatively thick LT plate 130 and a handling substrate (e.g., siliconsubstrate) 140 is formed or provided.

FIG. 9B shows a process step where the thickness of the relatively thickLT plate 130 is reduced to a thinner LT plate 144, so as to form anassembly 146. In some embodiments, such a thinning process step can beachieved by, for example, polishing process such as a mechanicalpolishing process, a chemical mechanical process, etc. In FIG. 9B, thethinner LT plate 144 is shown to include a first surface resulting fromthe thinning process step, and a second surface, opposite from the firstsurface, attached to the handling substrate 140.

FIG. 9C shows a process step where the first surface of the LT plate 144is attached to a quartz plate 112, so as to form an assembly 148. Insome embodiments, the first surface of the LT plate 144 can be attached(e.g., bonded) directly to the quartz plate 112, or through anintermediate layer.

FIG. 9D shows a process step where the handling substrate (140 in FIG.9C) is removed so as to partially or fully expose the LT plate 144, tothereby form an assembly 150. In some embodiments, such removal of thehandling substrate (such as a silicon substrate) can be achieved by, forexample, an etching process. In some embodiments, the LT plate 144 inthe assembly 150 of FIG. 9D may or may not be substantially the same asthe LT plate 144 in the assembly 148 of FIG. 9C. For the purpose ofdescription, it will be understood that the exposed surface resultingfrom the removal of the handling substrate is similar to the secondsurface of the LT plate 144 described in reference to FIG. 9B.

FIG. 9E shows a process step where an electrode 102 is formed on thesecond surface of the LT plate 144, so as to form an assembly 152. Asdescribed herein, such an electrode can include an interdigitizedarrangement of fingers 122 a, 122 b.

In some embodiments, some or all of the process steps associated withFIGS. 9A-9E can be implemented for an individual unit to produce asingle unit of the assembly 152, implemented for a plurality ofindividual units to produce a plurality of respective single units ofassemblies 152, implemented while a plurality units are attached in anarray format (e.g., wafer format) followed by singulation to produce aplurality of singulated units of assemblies 152, or some combinationthereof.

FIG. 10A shows a SAW resonator 100 that can be formed by either of theprocesses described in reference to FIGS. 8A-8C and FIGS. 9A-9E. If theprocess of FIGS. 8A-8C is utilized, the assembly 138 of FIG. 8C can bethe SAW resonator 100 of FIG. 10A. If the process of FIGS. 9A-9E isutilized, the assembly 152 of FIG. 9E can be the SAW resonator 100 ofFIG. 10A. For the purpose of description, the LT plate 104 having athickness d1 can be considered to be a thin LT plate. Example thicknessvalues and/or ranges of such a thin LT plate are provided herein.

FIG. 10B shows a SAW resonator 100 that can be formed by either of theprocesses described in reference to FIGS. 8A-8C and FIGS. 9A-9E. If theprocess of FIGS. 8A-8C is utilized, the assembly 138 of FIG. 8C can bethe SAW resonator 100 of FIG. 10B. If the process of FIGS. 9A-9E isutilized, the assembly 152 of FIG. 9E can be the SAW resonator 100 ofFIG. 10B. For the purpose of description, the LT plate 104 having athickness d2 can be considered to be a thick LT plate. Example thicknessvalues and/or ranges of such a thick LT plate are provided herein.

FIGS. 11A-11D show examples where a thick LT plate 104 b (with thicknessd2) can be preferable over a thin LT plate 104 a (with thickness d1). Insuch examples, the LT plates are depicted by themselves, however, itwill be understood that such LT plates can be attached to respectivesubstrates (e.g., handling substrate and/or quartz substrate). It willalso be understood that some or all of the effects in the examples ofFIGS. 11A-11D can be manifested for the respective LT plates, whether ornot such LT plates are attached to other parts.

For example, and referring to FIG. 11A, a thin LT plate 104 a istypically more susceptible to breakage than a thick LT plate 104 b, fora given application of force. In another example, and referring to FIG.11B, a thin LT plate 104 a is typically more susceptible to warpage thana thick LT plate 104 b, for a given warping condition.

It is noted that in some applications, performance of a SAW resonatormay depend on uniformity of thickness of an LT plate. Thus, andreferring to FIG. 11C, an LT plate may have a non-uniform thicknessresulting from, for example, a tilted thinning operation. For example,suppose that each of a thin LT plate 104 a and a thick LT plate 104 b issubjected to a similar tilted thinning operation, so as to result in awedge-shaped side profile. The thin LT plate 104 a is shown to have anaverage thickness value of d1, a high thickness value of d1+Δd, and alow thickness value of d1−Δd. Similarly, the thick LT plate 104 b isshown to have an average thickness value of d2, a high thickness valueof d2+Δd, and a low thickness value of d2−Δd. For each plate, relativeerror in thickness can be estimated as Δd/(average thickness). Thus, thethick LT plate 104 b will have a lower relative error in thickness thanthe thin LT plate 104 a, for a given thickness error condition Δd.

In the example of FIG. 11C, the thickness error condition Δd is assumedto be due to an error resulting from a thinning process. FIG. 11D showsthat even if such a thinning process yields a uniform average thicknessfor a plate, either or both surfaces of the plate can have imperfectionsresulting from, for example, the thinning process itself or a previousfabrication step related to the plate.

In FIG. 11D, such imperfections are depicted in an exaggerated mannerfor each surface of a thin LT plate 104 a (having an average thicknessd1), and for each surface of a thick LT plate 104 b (having an averagethickness d2). Assuming that each of such surfaces has an imperfectionerror of δ, relative error in thickness can be estimated as 2δ/(averagethickness). Thus, the thick LT plate 104 b will have a lower relativeerror in thickness than the thin LT plate 104 a, for a given surfaceimperfection error condition δ.

The foregoing examples described in reference to FIGS. 11A-11D show thata thick LT plate may be preferable over a thin LT plate. However, simplymaking an LT plate thicker can result in degradation of performance.

FIGS. 12-19 show four example SAW resonators with different combinationsof LT plates and electrodes. For example, FIG. 12 shows a SAW resonatorhaving an LT plate with a quartz plate attached on one side, and anelectrode formed on the other side. Referring to the dimensionalparameters shown in FIG. 7, the LT plate of FIG. 12 is shown to have athickness of T_(piezoelectric)=0.15λ, and the electrode, formed ofcopper, is shown to have a thickness of T_(electrode)=0.06λ.

FIG. 13 shows an impedance characteristic plot for the SAW resonator ofFIG. 12. In FIG. 13, resonant frequency f_(r) and antiresonant frequencyf_(a) are shown; and corresponding impedance values at such frequenciesare Z_(r) and Z_(a), respectively. For the example of FIGS. 12 and 13,impedance ratio (20 log(Z_(a)/Z_(r))) has a value of 78 dB, and there isessentially no in-band ripple, with little or no spurious responseobserved at higher frequencies.

In another example, FIG. 14 shows a SAW resonator having an LT platewith a quartz plate attached on one side, and an electrode formed on theother side. Referring to the dimensional parameters shown in FIG. 7, theLT plate of FIG. 14 is shown to have a thickness ofT_(piezoelectric)=3λ, and the electrode, formed of copper, is shown tohave a thickness of T_(electrode)=0.06λ.

FIG. 15 shows an impedance characteristic plot for the SAW resonator ofFIG. 14. In FIG. 15, resonant frequency f_(r) and antiresonant frequencyf_(a) are shown; and corresponding impedance values at such frequenciesare Z_(r) and Z_(a), respectively. For the example of FIGS. 14 and 15,impedance ratio (20 log(Z_(a)/Z_(r))) has a value that is lower than theexample of FIGS. 12 and 13, and there are larger in-band and out-of-bandripples. Accordingly, such performance characteristics make the SAWresonator of FIG. 14 not practical for many applications.

In yet another example, FIG. 16 shows a SAW resonator having an LT platewith a quartz plate attached on one side, and an electrode formed on theother side. Referring to the dimensional parameters shown in FIG. 7, theLT plate of FIG. 16 is shown to have a thickness ofT_(piezoelectric)=5λ, and the electrode, formed of copper, is shown tohave a thickness of T_(electrode)=0.1λ.

FIG. 17 shows an impedance characteristic plot for the SAW resonator ofFIG. 16. In FIG. 17, resonant frequency f_(r) and antiresonant frequencyf_(a) are shown; and corresponding impedance values at such frequenciesare Z_(r) and Z_(a), respectively. For the example of FIGS. 16 and 17,impedance ratio (20 log(Z_(a)/Z_(r))) has a value that is higher thanthe example of FIGS. 14 and 15, and there is little or no in-bandripple, but larger spurious responses at higher frequencies. Thus, theSAW resonator of FIG. 16 may not be practical for many applications.

In yet another example, FIG. 18 shows a SAW resonator having an LT platewith a quartz plate attached on one side, and an electrode formed on theother side. Referring to the dimensional parameters shown in FIG. 7, theLT plate of FIG. 18 is shown to have a thickness ofT_(piezoelectric)=50λ, and the electrode, formed of copper, is shown tohave a thickness of T_(electrode)=0.12λ.

FIG. 19 shows an impedance characteristic plot for the SAW resonator ofFIG. 18. In FIG. 19, resonant frequency f_(r) and antiresonant frequencyf_(a) are shown; and corresponding impedance values at such frequenciesare Z_(r) and Z_(a), respectively. For the example of FIGS. 18 and 19,impedance ratio (20 log(Z_(a)/Z_(r))) has a value that is similar to theexample of FIGS. 12 and 13, and there is essentially no in-band ripple,with some smaller amplitude spurious responses (that are acceptable inmany applications) observed at higher frequencies.

A number of observations can be made from the examples of FIGS. 12-19.First, suppose that the SAW resonator of FIG. 12 is an example where theLT plate is considered to be thin (T_(piezoelectric)=0.15λ), and theelectrode has an appropriate thickness (T_(electrode)=0.06λ) for thethin LT plate, such that the SAW resonator provides desirableperformance with no in-band ripple and little or no spurious responseobserved at higher frequencies. However, and referring to the SAWresonator of FIG. 14 where the LT plate thickness is increasedsignificantly to T_(piezoelectric)=3λ but the electrode thicknessremains the same at T_(electrode)=0.06λ, performance of the SAWresonator suffers greatly with large in-band and out-of-band ripples.Such a comparison shows that simply increasing the thickness of the LTplate can result in significant performance degradation.

Second, a comparison between the SAW resonator of FIG. 14(T_(piezoelectric)=3λ, T_(electrode)=0.06λ) and the SAW resonator ofFIG. 16 (T_(piezoelectric)=5λ, T_(electrode)=0.1λ) shows that anincrease in the electrode thickness (from 0.06λ to 0.1λ) results in asignificant improvement in performance, even if the LT plate thicknessis increased further (T_(piezoelectric)=3λ to T_(piezoelectric)=5λ).Such a comparison shows that an increase in electrode thickness can be afactor for improvement in performance for a thicker LT plate.

Third, a comparison between the SAW resonator of FIG. 16(T_(piezoelectric)=5λ, T_(electrode)=0.1λ) and the SAW resonator of FIG.18 (T_(piezoelectric)=50λ, T_(electrode)=0.12λ) shows that an increaseof 20% in the electrode thickness (from 0.1λ to 0.12λ) results in animprovement in performance, even if the LT plate thickness is increasedfurther by an order of magnitude (T_(piezoelectric)=5λ toT_(piezoelectric)=50λ). Such a comparison shows that either or both ofelectrode thickness and LT plate thickness can be factor(s) forimprovement in performance.

FIG. 20 shows impedance ratio plots as a function of LT plate thickness,for different copper (Cu) electrode thicknesses. More particularly,curve 170 is for a SAW resonator having a copper electrode with athickness T_(electrode) in a range of 0.06λ to 0.079λ (and thus includesthe examples of FIGS. 12 and 14). Curve 172 is for a SAW resonatorhaving a copper electrode with a thickness T_(electrode) of 0.08λ. Curve174 is for a SAW resonator having a copper electrode with a thicknessT_(electrode) of 0.25λ which is thicker than any of the copper electrodeexamples of FIGS. 12-19.

For each of the three curves (170, 172 or 174) of FIG. 20, thesolid-line portion corresponds to impedance ratio responses that arewithout (or sufficiently low amplitude) ripples or spurious responses(as a function of frequency) to make the corresponding SAW resonatorpractical for many applications, and the dashed-line portion correspondsto impedance ratio responses having either or both of ripples andspurious responses (as a function of frequency) to make thecorresponding SAW resonator impractical for many applications. Thus,example data point 176 on the curve 170, corresponding to theabove-described SAW resonator of FIG. 12, is considered to provideacceptable performance, and example data point 178 on the curve 170,corresponding to the above-described SAW resonator of FIG. 14, isconsidered to provide performance that is not acceptable for manyapplications.

A number of observations can be made from the impedance ratio plots ofFIG. 20. First, it is noted that for a copper electrode thickness up tosome value (e.g., at or around 0.079λ), impedance ratio is highest witha thin LT plate (e.g., 0.1λ), and decreases generally monotonically asthe LT plate thickness increases. In such a decreasing trend ofimpedance ratio, a range (e.g., 0λ to about 2λ) of LT plate thicknessprovides acceptable performance of the corresponding SAW resonator, anda thicker range (e.g., greater than 2λ) of the LT plate results in highripples and/or spurious responses so as to make the corresponding SAWresonator impractical for many applications. In the latterconfiguration, one can consider the LT plate to be too thick for thecorresponding copper electrode thickness.

Second, it is noted that for a copper electrode thickness greater thanthe above-discussed value (e.g., at or around 0.079λ), impedance ratiomay or may not be the highest with a thin LT plate (e.g., 0.1λ), andeventually reaches an approximately flat impedance ratio as the LT platethickness increases. For the purpose of description, such a copperelectrode thickness value (e.g., at or around 0.079λ) can be consideredto be a threshold thickness value.

When a copper electrode thickness is greater than, but close to, thethreshold value (e.g., as in the impedance ratio curve 172), theimpedance ratio has a highest value with a thin LT plate similar to theabove-discussed copper electrode thickness below the threshold value.However, the impedance ratio approximately flattens out at some LTthickness value (e.g., about 1λ), and generally remains approximatelyflat, as the LT thickness increases.

When a copper electrode thickness is significantly greater than thethreshold value, the impedance ratio may or may not have a highest valuewith a thin LT plate (e.g., 0.1λ). For example, the impedance ratiocurve 174 corresponding to a significantly larger copper electrodethickness of 0.25λ has an impedance ratio value at the thin LT platethickness of 0.1λ that is about the same as the flattened out impedanceratio value at higher LT thickness values. It is noted that in such aconfiguration (where the copper electrode thickness is significantlygreater than the threshold value), the impedance ratio also has anapproximately flat response beyond some LT thickness value (e.g., about1λ).

In the foregoing trends of impedance ratio of the curves 172 and 174, athicker range (e.g., greater than about 2λ) of LT plate providesacceptable performance of the corresponding SAW resonator in terms ofacceptable ripples and spurious responses, and a thinner range (e.g.,0.1λ to 2λ) of the LT plate results in ripples and/or spurious responsesso as to make the corresponding SAW resonator impractical for manyapplications. In the latter configuration, one can consider the LT plateto be too thin for the corresponding copper electrode thickness.

Based on the foregoing description of the examples of FIG. 20, one cansee that depending on the thickness of a given LT plate, an electrodethickness can be selected or tuned to provide desired performance in thecorresponding SAW resonator. For example, if an LT plate is thinner thansome thickness value, a thinner electrode (e.g., thickness less than athreshold electrode thickness value) can be provided such that thecorresponding SAW resonator has an acceptable performance. In anotherexample, if an LT plate is thicker than some thickness value, a thickerelectrode (e.g., thickness greater than the threshold electrodethickness value) can be provided such that the corresponding SAWresonator has an acceptable performance.

Referring to FIG. 20, it is noted that for the copper electrodethickness range of 0.06λ to 0.079λ, higher impedance ratios of 70 to 78dB can be obtained for the LT plate thickness in the range of 0.1λ toabout 1.3λ, and slightly lower impedance ratios of 68 to 70 dB can beobtained at the LT plate thickness range of 1.3λ to about 2λ, withlittle or no ripple or spurious response similar to the example of FIG.12. For the copper electrode thickness range of 0.08λ to 0.25λ,impedance ratios of 71 to 73 dB (e.g., 72 to 73 dB for the copperelectrode thickness of 0.08λ, and 71 dB for the copper electrodethickness of 0.25λ) can be obtained for the LT plate thickness in therange of about 2λ to about 200λ, with sufficiently small spuriousresponses (similar to the example of FIG. 18) so as to make thecorresponding SAW resonator usable in many applications.

In the various examples described herein in reference to FIGS. 12-20,the electrodes are copper electrodes having various thicknesses.Assuming that such electrodes have similar layout dimensions, a thickercopper electrode has more mass than a thinner electrode. Accordingly, anelectrode having an increased mass can be utilized to provide a desiredperformance for a SAW resonator having an increased thickness of an LTplate.

It is noted that copper is an example material that can be utilized asan electrode for a SAW resonator. Other electrically conductivematerials such as metals and/or alloys can also be utilized as SAWresonator electrodes. For example, FIG. 21 shows a summary of impedanceratio plots as a function of LT plate thickness, for different aluminum(Al) electrode thicknesses. More particularly, curve 180 is for a SAWresonator having an aluminum electrode with a thickness T_(electrode) ina range of 0.081λ to 0.148λ; curve 182 is for a SAW resonator having analuminum electrode with a thickness T_(electrode) of 0.15λ; and curve184 is for a SAW resonator having an aluminum electrode with a thicknessT_(electrode) of 0.35λ.

For each of the three curves (180, 182 or 184) of FIG. 21, thesolid-line portion corresponds to impedance ratio responses that arewithout (or sufficiently low amplitude) ripples or spurious responses(as a function of frequency) to make the corresponding SAW resonatorpractical for many applications, and the dashed-line portion correspondsto impedance ratio responses having either or both of ripples andspurious responses (as a function of frequency) to make thecorresponding SAW resonator impractical for many applications.

A number of observations can be made from the impedance ratio plots ofFIG. 21. First, it is noted that for an aluminum electrode thickness upto some value (e.g., at or around a value of 0.148λ), impedance ratio ishighest with a thin LT plate (e.g., 0.1λ), and decreases generallymonotonically as the LT plate thickness increases. In such a decreasingtrend of impedance ratio, a range (e.g., 0.1λ to about 2λ) of LT plateprovides acceptable performance of the corresponding SAW resonator, anda thicker range (e.g., greater than 2λ) of the LT plate results in highripples and/or spurious responses so as to make the corresponding SAWresonator impractical for many applications. In the latterconfiguration, one can consider the LT plate to be too thick for thecorresponding aluminum electrode thickness.

Second, it is noted that for an aluminum electrode thickness greaterthan the above-discussed value (e.g., at or around a value of 0.148λ),impedance ratio may or may not be the highest with a thin LT plate(e.g., 0.1λ), and eventually reaches an approximately flat impedanceratio as the LT plate thickness increases. For the purpose ofdescription, an aluminum electrode thickness value (e.g., at or around avalue of 0.148λ) can be considered to be a threshold thickness value.

When an aluminum electrode thickness is greater than, but close to, thethreshold value, the impedance ratio has a highest value with a thin LTplate similar to the above-discussed aluminum electrode thickness belowthe threshold value. However, the impedance ratio approximately flattensout at some LT thickness value (e.g., about 1λ), and generally remainsapproximately flat, as the LT thickness increases. Each of the impedanceratio curves 182, 184 is an example of such an impedance ratio profile.

When an aluminum electrode thickness is significantly greater than thethreshold value, the impedance ratio may or may not have a highest valuewith a thin LT plate (e.g., 0.1λ). For example, if an aluminum electrodehas a thickness that is significantly greater than 0.35λ (of the curve184), a corresponding impedance ratio curve likely has an impedanceratio value at the thin LT plate thickness of 0λ that is about the sameas the flattened out impedance ratio value at higher LT thicknessvalues.

In the foregoing examples of impedance ratio of the curves 182 and 184,a thicker range (e.g., greater than about 2λ) of LT plate providesacceptable performance of the corresponding SAW resonator in terms ofacceptable ripples and spurious responses, and a thinner range (e.g., 0λto 2λ) of the LT plate results in ripples and/or spurious responses soas to make the corresponding SAW resonator impractical for manyapplications. In the latter configuration, one can consider the LT plateto be too thin for the corresponding aluminum electrode thickness.

Referring to FIG. 21, it is noted that for the aluminum electrodethickness range of 0.081λ to 0.148λ, higher impedance ratios of 70 to78.5 dB can be obtained for the LT plate thickness in the range of 0λ toabout 1.3λ, and slightly lower impedance ratios of 67.5 to 70 dB can beobtained at the LT plate thickness range of 1.3λ to about 2λ, withlittle or no ripple or spurious response. For the aluminum electrodethickness range of 0.15λ to 0.35λ, larger out-of-band spurious responsesare observed for LT plate thickness in a range of 0λ to about 2λ;however, for LT plate thickness in a range of 2λ to 200λ, impedanceratios of 71 to 72 dB can be obtained with sufficiently small spuriousresponses so as to make the corresponding SAW resonator usable in manyapplications. It is noted that such a range of impedance ratios (71 to72 dB) are greater by about 6 to 8 dB than the impedance ratio of about65 dB obtained by a common SAW resonator having a thin aluminumelectrode.

In another example, an electrode formed from gold (Au) having athickness T_(electrode) in a range of 0.02λ to 0.036λ can provideimpedance ratios of 68 to 78 dB, for an LT plate thickness in a range of0λ to 2λ, with little or no ripple or spurious response to make thecorresponding SAW resonator practical for many applications. For such anelectrode thickness, when the LT plate is thicker, either or both ofripples and spurious responses are present so as to make thecorresponding SAW resonator impractical for many applications.

On the other hand, for a gold electrode having a thickness T_(electrode)in a range of 0.037λ to 0.12λ, impedance ratios of 70 dB or greater canbe obtained with little or no ripple and with small spurious responsesto make the corresponding SAW resonator practical for many applications,for an LT plate thickness greater than 2λ (e.g., 2λ to 200λ). For suchan electrode thickness, when the LT plate is thinner, either or both ofripples and spurious responses are present so as to make thecorresponding SAW resonator impractical for many applications.

Based on the foregoing description of the examples of FIGS. 20 and 21and the gold electrode configuration, one can see that depending on thethickness of a given LT plate, an electrode's mass can be selected ortuned to provide desired performance in the corresponding SAW resonator.Such a mass can be selected based on, for example, density of theelectrode and/or dimensions of the electrode. In some embodiments,density of an electrode can be selected based on the material of theelectrode. In some embodiments, dimensions of an electrode can beselected based on the thickness of the electrode.

FIG. 22 shows impedance ratio plots (as a function of piezoelectricthickness) for a SAW resonator with a more generalized combination of apiezoelectric plate (e.g., LT or LN plate) and an electrode (e.g., metalelectrode) implemented thereon. More particularly, an impedance ratiocurve 191 is for an electrode having a thickness T_(electrode) that isless than or equal to a thickness threshold value T_(threshold), and animpedance ratio curve 192 is for an electrode having a thicknessT_(electrode) that is greater than the thickness threshold valueT_(threshold). Examples of such a thickness threshold valueT_(threshold) are described herein in greater detail.

Similar the examples of FIGS. 20 and 21, in the example of FIG. 22, thesolid-line portion of each of the curves 191, 192 corresponds toimpedance ratio responses that are without (or sufficiently lowamplitude) ripples or spurious responses to make the corresponding SAWresonator practical for many applications, and the dashed-line portioncorresponds to impedance ratio responses having either or both ofripples and spurious responses to make the corresponding SAW resonatorimpractical for many applications.

As seen in the examples of FIGS. 20 and 21 and the gold electrodeconfiguration, and also referring to FIG. 22, there is a thickness valueT_(threshold) such that an electrode thinner than or equal toT_(threshold) (as in the curve 191) results in the corresponding SAWresonator to provide a solid-line performance (without (or sufficientlylow amplitude) ripples or spurious responses) for a thin piezoelectric(also referred to herein as a piezo) having a thickness less than orequal to T1_(piezo), and a dashed-line performance (either or both ofripples and spurious responses) for a thick piezoelectric having athickness less than T1_(piezo). Further, an electrode thicker thanT_(threshold) (as in the curve 192) results in the corresponding SAWresonator to provide a solid-line performance (without (or sufficientlylow amplitude) ripples or spurious responses) for a thick piezoelectrichaving a thickness greater than T2_(piezo), and a dashed-lineperformance (either or both of ripples and spurious responses) for athin piezoelectric having a thickness less than or equal to T2_(piezo).

It is noted that the thickness values T1_(piezo) and T2_(piezo) may ormay not be the same; however for the purpose of description of somespecific examples, such values are assumed to be approximately the same.Table 1 lists such piezoelectric thickness valuesT_(piezo)≈T1_(piezo)≈T2_(piezo), as well as electrode T_(threshold)values, for the examples associated with copper, aluminum and goldelectrodes.

TABLE 1 Piezoelectric Electrode material material T_(piezo) ≈ T1_(piezo)≈ T2_(piezo) T_(threshold) Copper (Cu) LT 2λ 0.079λ Aluminum (Al) LT 2λ0.148λ Gold (Au) LT 2λ 0.036λ

In the examples of Table 1, the piezoelectric material is LT, and thecorresponding values of T_(piezo) for such LT material, as well asT_(threshold) values of different metal electrodes are listed. It willbe understood that values for T_(piezo) and T_(threshold) can beobtained for other piezoelectric materials, including LN material. Itwill also be understood that T_(piezo) may or may not bematerial-dependent, and T_(threshold) may or may not bematerial-dependent. For example, for SAW resonators utilizing LN plates,the thickness value T_(piezo) may or may not be similar to the thicknessvalue associated with LT plates. Also, for such LN plate based SAWresonators, T_(threshold) values of different metal electrodes may ormay not be similar to those associated with LT plate based SAWresonators.

In some embodiments, for the purpose of description, a piezoelectriclayer (also referred to herein as a piezoelectric plate, a piezoelectricfilm, or simply a piezoelectric or piezo) can be considered to be a thinpiezoelectric layer if its thickness is less than or equal to T_(piezo),and a thick piezoelectric layer if its thickness is greater thanT_(piezo). Also for the purpose of description, an electrodecorresponding to the foregoing piezoelectric layer can be considered athin electrode if its thickness is less than or equal to T_(threshold),and a thick electrode if its thickness is greater than T_(threshold).

As described herein, an electrode for a SAW resonator can be formed froma number of electrically conductive materials, including metals such ascopper, aluminum and gold. It will be understood that other electricallyconductive materials, including other metals, alloys, etc. can also beutilized as electrodes for SAW resonators having one or more features asdescribed herein. Table 2 lists non-limiting examples of metals that canbe utilized as such electrodes.

TABLE 2 Metal Density (g/cm³) Magnesium (Mg) 1.74 Aluminum (Al) 2.60Titanium (Ti) 4.51 Nickel (Ni) 8.90 Copper (Cu) 8.96 Molybdenum (Mo)10.2 Silver (Ag) 10.5 Hafnium (Hf) 13.3 Tantalum (Ta) 16.4 Tungsten (W)19.25 Gold (Au) 19.30 Platinum (Pt) 21.5

As described herein in reference to FIGS. 20-22 and Table 1, thicknessthreshold value T_(threshold) of an electrode decreases as density ofthe electrode material increases. FIG. 23 depicts such a relationshipfor the aluminum, copper and gold examples. It is noted that such datapoints may be parts of a curve 194 representative of electrode thicknessthreshold value T_(threshold) as a function of mass density of theelectrode material. Such a curve, and/or a set of data pointsrepresentative of such a curve, may be obtained by, for example,empirical measurements, calculation, extrapolation, interpolation,modelling, etc. It is also noted that such a curve, and/or a set of datapoints representative of such a curve, may be obtained for one or morepiezoelectric materials. For example, one set of T_(threshold) valuesmay be obtained and be applicable for both of LT and LN materials. Inanother example, a first set of T_(threshold) values may be utilized forLT material, and a second set of T_(threshold) values may be utilizedfor LN material.

FIG. 24 shows electrode thickness threshold values T_(threshold) ascircles, for the electrode materials listed in Table 2. In someembodiments, such T_(threshold) values can be represented by a curve(194 in FIG. 23) according to Equation 1.

$\begin{matrix}{T_{threshold} = {{\left( \frac{0.5}{MR} \right)\left\lbrack {a - {b\left( {1 - e^{{- \rho}\text{/}c}} \right)}} \right\rbrack}.}} & (1)\end{matrix}$In Equation 1, T_(threshold) is in terms of the wavelength λ associatedwith the electrode, ρ is the mass density (in g/cm³) of the electrodematerial, and MR is the metallization ratio of the electrode asdescribed herein (MR=F/(F+G)). For the example of FIG. 24 and Table 2,the parameters a, b and c have the following approximate values:a≈0.19091, b≈0.17658, and c≈9.08282, with a and b being in terms of A,and c being in terms of mass density ρ.

It is noted that if the metallization ratio MR of a given electrode is0.5 (as in the various examples associated with FIGS. 12-21), theT_(threshold) expression of Equation 1 can be reduced to Equation 2.T _(threshold) =a−b(1−e ^(−ρ/c)),  (2)with the parameters a, b, c and ρ being as described above in referenceto Equation 1.

In some embodiments, T_(threshold) can be calculated according toEquation 1 or Equation 2 with one or more variations from the foregoingspecific example values of the parameters a, b and c. For example, ifthe foregoing example value of a is considered to be a₀=0.19091, theparameter a can have a value of a=a₀+0.10a₀, a=a₀±0.09a₀, a=a₀±0.08a₀,a=a₀±0.07a₀, a=a₀±0.06a₀, a=a₀+0.05a₀, a=a₀±0.04a₀, a=a₀±0.03a₀,a=a₀±0.02a₀, or a=a₀±0.01a₀. Similarly, if the foregoing example valueof b is considered to be b₀=0.17658, the parameter b can have a value ofb=b₀±0.10b₀, b=b₀±0.09b₀, b=b₀±0.08b₀, b=b₀±0.07b₀, b=b₀+0.06b₀,b=b₀±0.05b₀, b=b₀±0.04b₀, b=b₀±0.03b₀, b=b₀±0.02b₀, or b=b₀ 0.01b₀.Similarly, if the foregoing example value of c is considered to bec₀=9.08282, the parameter c can have a value of c=c₀±0.10c₀,c=c₀±0.09c₀, c=c₀±0.08c₀, c=c₀±0.07c₀, c=c₀±0.06c₀, c=c₀±0.05c₀,c=c₀±0.04c₀, c=c₀±0.03c₀, c=c₀ 0.02c₀, or c=c₀±0.01c₀.

In some embodiments, if the T_(threshold) curve of Equation 1 orEquation 2 is considered to be T⁰ _(threshold) when using the specificexample values of a₀=0.19091, b₀=0.17658, and c₀=9.08282, aT_(threshold) curve can vary for designing a thickness of an electrode.For example, a T_(threshold) curve can vary in a range according toT_(threshold)=T⁰ _(threshold)±0.10T⁰ _(threshold), T_(threshold)=T⁰_(threshold)±0.09T⁰ _(threshold), T_(threshold)=T⁰ _(threshold)+0.08T⁰_(threshold), T_(threshold)=T⁰ _(threshold)±0.07T⁰ _(threshold),T_(threshold)=T⁰ _(threshold)±0.06T⁰ _(threshold), T_(threshold)=T⁰_(threshold)±0.05T⁰ _(threshold), T_(threshold)=T⁰ _(threshold)±0.04T⁰_(threshold), T_(threshold)=T⁰ _(threshold)±0.03T⁰ _(threshold),T_(threshold)=T⁰ _(threshold)±0.02T⁰ _(threshold), or T_(threshold)=T⁰_(threshold)+0.01T⁰ _(threshold).

As described herein, by using an electrode thicker than theT_(threshold) value, good or acceptable frequency characteristicperformance can be obtained for a SAW resonator having a piezoelectricplate thicker than, for example, 2λ. If a material is listed in Table 2,the corresponding T_(threshold) value can be utilized to design anelectrode having a thickness, for example, greater than T_(threshold).If a material is not listed in Table 2, the corresponding T_(threshold)value can be calculated according to Equation 1 or Equation 2, and sucha threshold value can be utilized to design an electrode having athickness, for example, greater than T_(threshold).

In some embodiments, an electrode having one or more features asdescribed herein can be formed as an alloy of a plurality of elementssuch as plurality of metal elements. For such an electrode,T_(threshold) value can be calculated according to Equation 1 orEquation 2, using an average density of the alloy as the mass density p.Such a threshold value can be utilized to design an electrode having athickness, for example, greater than T_(threshold).

In some embodiments, an electrode having one or more features asdescribed herein can be formed to include a plurality of layers (e.g., aplurality of different materials). For such an electrode, T_(threshold)value can be calculated according to Equation 1 or Equation 2, using anaverage density of the plurality of layers as the mass density ρ. Such athreshold value can be utilized to design an electrode having athickness, for example, greater than T_(threshold).

Referring to FIGS. 23 and 24, in some embodiments, for a given electrodematerial, an electrode can be considered a thin electrode if itsthickness is less than or equal to a corresponding T_(threshold) value,and a thick electrode if its thickness is greater than the correspondingT_(threshold) value. For the purpose of description, such aT_(threshold) value may be a value that is measured or calculated, or avalue that is modelled, extrapolated or interpolated.

Accordingly, in the example of FIG. 23, the curve 194 and the regionunderneath the curve 194 can be considered to be representative of thinelectrodes for respective mass density materials, and the region abovethe curve 194 can be considered to be representative of thick electrodesfor respective mass density materials. Similarly, in the example of FIG.24, the curve represented by Equation 1 or Equation 2 and the regionunderneath the curve can be considered to be representative of thinelectrodes for respective mass density materials, and the region abovethe curve can be considered to be representative of thick electrodes forrespective mass density materials.

In some embodiments, a piezoelectric layer (also referred to herein as apiezoelectric plate, a piezoelectric film, or simply a piezoelectric orpiezo) can be considered to be a thick piezoelectric layer if itsthickness is greater than T_(piezo), greater than 1.01T_(piezo), greaterthan 1.02T_(piezo), greater than 1.03T_(piezo), greater than1.04T_(piezo), greater than 1.05T_(piezo), greater than 1.10T_(piezo),greater than 1.20T_(piezo), greater than 1.30T_(piezo), greater than1.40T_(piezo), greater than 1.50T_(piezo), or greater than 2T_(piezo).

In some embodiments, an electrode can be considered to be a thickelectrode if its thickness is greater than T_(threshold), greater than1.01T_(threshold), greater than 1.02T_(threshold), greater than1.03T_(threshold), greater than 1.04T_(threshold), greater than1.05T_(threshold), greater than 1.10T_(threshold), greater than1.20T_(threshold), greater than 1.30T_(threshold), greater than1.40T_(threshold), greater than 1.50T_(threshold), or greater than2T_(threshold).

Various specific examples provided herein are described in the contextof some specific configurations of the respective SAW resonators. Forexample, various examples described in reference to FIGS. 12-21 arebased on electrodes having a metallization ratio (MR) of 0.5, whereMR=F/(F+G), with F being a width of an electrode finger and G being agap dimension between two electrode fingers, as shown in FIG. 7.

Since at least the dimension F affects the size of an electrode and thusthe mass of the electrode, in some embodiments, one or more features ofthe present disclosure can also be implemented based on the metal ratio(MR). For example, an electrode can be provided with a desirable mass(also referred to herein as mass-loaded) based on a relationship(MR)×T_(electrode)=(constant). In such a configuration, if mass ratio ofan electrode is increased, then a reduced-thickness of the electrode canbe utilized, even for a thick piezoelectric layer.

In another example, various electrode examples are described as beingformed from materials such as metals and alloys. It will be understoodthat an electrode having one or more features of the present disclosurecan be implemented in one or more layers utilizing one or morematerials. If an electrode is formed in a plurality of layers with morethan one material, an effective mass density (or an equivalentmass-related parameter) can be utilized based on individual massdensities of the materials.

In yet another example, various examples described in reference to FIGS.12-21 are based on combinations of LT and quartz substrate. It will beunderstood that one or more features of the present disclosure can alsobe implemented utilizing other combinations of piezoelectric materialsand substrates. For example, a combination of LN and quartz substratecan be utilized to obtain functionalities with a mass-loaded electrode,similar to the LT/quartz combination.

It is noted that in the examples of FIGS. 12-20 (LT/quartz combinationwith copper electrodes), electrodes are formed on a combination of (0°,110°, 0°) LT/(0°, 132°45′, 90°) quartz structure substrate, where (φ, θ,ψ) represents Euler angles. For the examples of FIG. 21 (LT/quartzcombination with aluminum electrodes), electrodes are also formed on acombination of (0°, 110°, 0°) LT/(0°, 132° 45′, 90°) quartz structuresubstrate. It will be understood that other structures of LT and/orquartz substrate can also be utilized. For example, orientation anglesof (0−/+5°, 80 to 155°, 0−/+5°), (90−/+5°, 90−/+5°, 0 to 180°), andorientation angles equivalent thereof, may be utilized for LT to providea desired electromechanical coupling property.

If LN is used instead of LT in combination with quartz, differentorientation angles can be utilized. For example, orientation angles of(0−/+5°, 60 to 160°, 0−/+5°), (90−/+5°, 90−/+5°, 0 to 180°), andorientation angles equivalent thereof, may be utilized for LN to providea desired electromechanical coupling property.

It is also noted that in some embodiments, orientation angles for thequartz substrate can be selected to not allow propagation direction ofthe SAW resonator to be oblique and power flow angle be approximatelyzero. For example, orientations such as the following can be utilizedfor the quartz substrate: (0+/−5°, θ, 35°+/−8°), (10°+/−±5°, θ,42°+/−8°), (20°+/−5°, θ, 50°+/−8°), (0°+/−5°, θ, 0°+/−5°), (10°+/−5°, θ,0°+/−5°), (20°+/−5°, θ, 0+/−5°), (0°+/−5°, θ, 90°+/−5°), (10°+/−5°, θ,90°+/−5°), (20°+/−5°, θ, 90°+/−5°), and (90°+/−5°, 90°+/−5°, L), whereeach of θ and ψ has a value in a range 0° to 180°.

In some embodiments, a SAW resonator having one or more features asdescribed herein can be implemented as a product, and such a product canbe included in another product. Examples of such different products aredescribed in reference to FIGS. 25-29.

FIG. 25 shows that in some embodiments, multiple units of SAW resonatorscan be fabricated while in an array form. For example, a wafer 200 caninclude an array of units 100′, and such units can be processed througha number of process steps while joined together. For example, in someembodiments, all of the process steps of FIGS. 8A-8C can be achievedwhile an array of such units are joined together as a wafer havingdifferent layers (e.g., quartz layer 112 and LT layer 130, 134). Inanother example, all of the process steps of FIGS. 9A-9E can be achievedwhile an array of such units are joined together as a wafer havingdifferent layers (e.g., handle layer 140, LT layer 130, 144 and quartzlayer 112).

Upon completion of process steps in the foregoing wafer format, thearray of units 100′ can be singulated to provide multiple SAW resonators100. FIG. 25 depicts one of such SAW resonators 100. In the example ofFIG. 25, the singulated SAW resonator 100 is shown to include anelectrode 102 formed on a piezoelectric layer 104 such as an LT layer.Such electrode and piezoelectric layer can be configured as describedherein to provide desirable features. It will be understood that in someembodiments, another electrode can be provided, as well as one or morereflectors, on the piezoelectric layer.

FIG. 26 shows that in some embodiments, a SAW resonator 100 having ormore features as described herein can be implemented as a part of apackage device 300. Such a packaged device can include a packagingsubstrate 302 configured to receive and support one or more components,including the SAW resonator 100.

FIG. 27 shows that in some embodiments, the SAW resonator based packageddevice 300 of FIG. 26 can be a packaged filter device 300. Such a filterdevice can include a packaging substrate 302 suitable for receiving andsupporting a SAW resonator 100 configured to provide a filteringfunctionality such as RF filtering functionality.

FIG. 28 shows that in some embodiments, a radio-frequency (RF) module400 can include an assembly 406 of one or more RF filters. Suchfilter(s) can be SAW resonator based filter(s) 100, packaged filter(s)300, or some combination thereof. In some embodiments, the RF module 400of FIG. 28 can also include, for example, an RF integrated circuit(RFIC) 404, and an antenna switch module (ASM) 408. Such a module canbe, for example, a front-end module configured to support wirelessoperations. In some embodiments, some of all of the foregoing componentscan be mounted on and supported by a packaging substrate 402.

In some implementations, a device and/or a circuit having one or morefeatures described herein can be included in an RF device such as awireless device. Such a device and/or a circuit can be implementeddirectly in the wireless device, in a modular form as described herein,or in some combination thereof. In some embodiments, such a wirelessdevice can include, for example, a cellular phone, a smart-phone, ahand-held wireless device with or without phone functionality, awireless tablet, etc.

FIG. 29 depicts an example wireless device 500 having one or moreadvantageous features described herein. In the context of a modulehaving one or more features as described herein, such a module can begenerally depicted by a dashed b₀×400, and can be implemented as, forexample, a front-end module (FEM). In such an example, one or more SAWfilters as described herein can be included in, for example, an assemblyof filters such as duplexers 526.

Referring to FIG. 29, power amplifiers (PAs) 520 can receive theirrespective RF signals from a transceiver 510 that can be configured andoperated in known manners to generate RF signals to be amplified andtransmitted, and to process received signals. The transceiver 510 isshown to interact with a baseband sub-system 408 that is configured toprovide conversion between data and/or voice signals suitable for a userand RF signals suitable for the transceiver 510. The transceiver 510 canalso be in communication with a power management component 506 that isconfigured to manage power for the operation of the wireless device 500.Such power management can also control operations of the basebandsub-system 508 and the module 400.

The baseband sub-system 508 is shown to be connected to a user interface502 to facilitate various input and output of voice and/or data providedto and received from the user. The baseband sub-system 508 can also beconnected to a memory 504 that is configured to store data and/orinstructions to facilitate the operation of the wireless device, and/orto provide storage of information for the user.

In the example wireless device 500, outputs of the PAs 520 are shown tobe routed to their respective duplexers 526. Such amplified and filteredsignals can be routed to an antenna 516 through an antenna switch 514for transmission. In some embodiments, the duplexers 526 can allowtransmit and receive operations to be performed simultaneously using acommon antenna (e.g., 516). In FIG. 29, received signals are shown to berouted to “Rx” paths (not shown) that can include, for example, alow-noise amplifier (LNA).

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While some embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A surface acoustic wave device for providingresonance of a surface acoustic wave having a wavelength λ, comprising:a quartz substrate; a piezoelectric plate formed from LiTaO₃ or LiNbO₃and disposed over the quartz substrate, the piezoelectric plate having athickness greater than 2λ; and an interdigital transducer electrodeformed over the piezoelectric plate, the interdigital transducerelectrode having a mass density ρ in a range 1.50 g/cm³<ρ≤6.00 g/cm³,6.00 g/cm³<ρ≤12.0 g/cm³, or 12.0 g/cm³<ρ≤23.0 g/cm³, and a thicknessgreater than 0.148λ, greater than 0.079λ, or greater than 0.036λ,respectively.
 2. The surface acoustic wave device of claim 1 wherein theinterdigital transducer electrode has a metallization ratio (MR) ofapproximately 0.5, where MR=F/(F+G), F being a width of an electrodefinger and G being a gap dimension between two interdigitizedneighboring fingers of the interdigital transducer electrode.
 3. Thesurface acoustic wave device of claim 1 wherein the interdigitaltransducer electrode includes aluminum, titanium, magnesium, copper,nickel, silver, molybdenum, gold, platinum, tungsten, tantalum, hafnium,an alloy formed from a plurality of metals, or a structure having aplurality of layers, with a mass density range 1.50 g/cm³<ρ≤23.0 g/cm³.4. The surface acoustic wave device of claim 1 wherein the piezoelectricplate is a LiTaO₃ (LT) plate.
 5. The surface acoustic wave device ofclaim 4 wherein the LT plate is configured with Euler angles of (0−/+5°,80 to 155°, 0−/+5°), (90−/+5°, 90°−/+5°, 0 to 180°).
 6. The surfaceacoustic wave device of claim 1 wherein the piezoelectric plate is aLiNbO₃ (LN) plate.
 7. The surface acoustic wave device of claim 6wherein the LN plate is configured with Euler angles of (0−/+5°, 60 to160°, 0−/+5°), (90−/+5°, 90°−/+5°, 0 to 180°).
 8. The surface acousticwave device of claim 1 wherein the quartz substrate is configured withEuler angles of (0+/−5°, θ, 35°+/−8°), (10°+/−±5°, θ, 42°+/−8°),(20°+/−5°, θ, 50°+/−8°), (0°+/−5°, θ, 0°+/−5°), (10°+/−5°, θ, 0°+/−5°),(20°+/−5°, θ, 0°+/−5°), (0°+/−5°, θ, 90°+/−5°), (10°+/−5°, θ, 90°+/−5°),(20°+/−5°, θ, 90°+/−5°), (90°+/−5°, 90°+/−5°, ψ), where each of θ and ψhas a value in a range 0° to 180°.
 9. A method for manufacturing asurface acoustic wave device that provides resonance of a surfaceacoustic wave having a wavelength A, the method comprising: forming orproviding a quartz substrate; implementing a piezoelectric plate formedfrom LiTaO₃ or LiNbO₃ to be over the quartz substrate, such that thepiezoelectric plate has a thickness greater than 2λ; and forming aninterdigital transducer electrode over the piezoelectric plate, suchthat the interdigital transducer electrode has a mass density ρ in arange 1.50 g/cm³<ρ≤6.00 g/cm³, 6.00 g/cm³<ρ≤12.0 g/cm³, or 12.0g/cm³<ρ≤23.0 g/cm³, and a thickness greater than 0.148λ, greater than0.079λ, or greater than 0.036λ, respectively.
 10. The method of claim 9wherein the implementing of the piezoelectric plate includes forming orproviding an assembly of a thick piezoelectric plate and a quartz plate,the quartz plate providing the quartz substrate for the piezoelectricplate.
 11. The method of claim 10 wherein the implementing of thepiezoelectric plate further includes performing a thinning process onthe thick piezoelectric plate to provide the piezoelectric plate withthe thickness greater than 2λ, such that the piezoelectric plateincludes a first surface that engages with the quartz plate and a secondsurface, opposite from the first surface, resulting from the thinningprocess.
 12. The method of claim 9 wherein the implementing of thepiezoelectric plate includes forming or providing an assembly of a thickpiezoelectric plate and a handling substrate.
 13. The method of claim 12wherein the implementing of the piezoelectric plate further includesperforming a thinning process on the thick piezoelectric plate toprovide a thinned piezoelectric plate with a thickness greater than 2λ,such that the thinned piezoelectric plate includes a first surfaceresulting from the thinning process and a second surface, opposite fromthe first surface, that engages the handling substrate.
 14. The methodof claim 13 wherein the implementing of the piezoelectric plate furtherincludes attaching a quartz plate to the first surface of the thinnedpiezoelectric plate such that the quartz plate provides the quartzsubstrate.
 15. The method of claim 14 wherein the implementing of thepiezoelectric plate further includes removing the handling substrate toexpose the second surface of the thinned piezoelectric plate, and thethinned piezoelectric plate with the exposed second surface provides thepiezoelectric plate.
 16. A surface acoustic wave device for providingresonance of a surface acoustic wave having a wavelength A, comprising:a quartz substrate; a piezoelectric plate formed from LiTaO₃ or LiNbO₃and disposed over the quartz substrate, the piezoelectric plate having athickness greater than 2λ; and an interdigital transducer electrodeformed over the piezoelectric plate, the interdigital transducerelectrode having a mass density ρ and a thickness T greater than${T_{threshold} = {\left( \frac{0.5}{MR} \right)\left\lbrack {a - {b\left( {1 - e^{{- \rho}\text{/}c}} \right)}} \right\rbrack}},$MR being a metallization ratio of the interdigital transducer electrode,a having a value of 0.19091λ±δ_(a), b having a value of 0.17658λ±δ_(b),and c having a value of 9.08282 g/cm³±δ_(c).
 17. The surface acousticdevice of claim 16 wherein the metallization ratio (MR) has a value ofapproximately 0.5.
 18. The surface acoustic device of claim 16 whereinδ_(a) has a value of (0.10)0.19091λ, (0.09)0.19091λ, (0.08)0.19091λ,(0.07)0.19091λ, (0.06)0.19091λ, (0.05)0.19091λ, (0.04)0.19091λ,(0.03)0.19091λ, (0.02)0.19091λ, (0.01)0.19091λ, or less than(0.01)0.19091λ.
 19. The surface acoustic device of claim 16 whereinδ_(b) has a value of (0.10)0.17658λ, (0.09)0.17658λ, (0.08)0.17658λ,(0.07)0.17658λ, (0.06)0.17658λ, (0.05)0.17658λ, (0.04)0.17658λ,(0.03)0.17658λ, (0.02)0.17658λ, (0.01)0.17658λ, or less than(0.01)0.17658λ.
 20. The surface acoustic device of claim 16 whereinδ_(c) has a value of (0.10)9.08282 g/cm³, (0.09)9.08282 g/cm³,(0.08)9.08282 g/cm³, (0.07)9.08282 g/cm³, (0.06)9.08282 g/cm³,(0.05)9.08282 g/cm³, (0.04)9.08282 g/cm³, (0.03)9.08282 g/cm³,(0.02)9.08282 g/cm³, (0.01)9.08282 g/cm³, or less than (0.01)9.08282g/cm³.